Field of the Invention
The present invention relates to an imprint apparatus, a mold, an imprint method, and a method of manufacturing an article.
Description of the Related Art
An imprint technique is a technique capable of transferring a nanoscale micropattern, and has received attention as one of nanolithography techniques for mass producing semiconductor devices and magnetic storage media. In the imprint apparatus using the imprint technique, a mold (original) on which a fine three-dimensional pattern has been formed is brought into contact with (pressed against) an imprint material on a substrate. Then, the mold is released after the imprint material on the substrate is cured in a state in which the mold and the imprint material are in contact with each other, thereby forming a pattern on the substrate.
In the imprint apparatus, it is necessary, in order to form the pattern, to bring the mold into contact with the imprint material or release the mold from the imprint material. Therefore, the life of the mold is a big issue. One of major factors that influences the life of the mold is particles generated in the imprint apparatus. The particles are attached to the obverse surface of the substrate and the pattern surface of the mold. Therefore, if the mold is brought into contact with the imprint material on the substrate in that state, the pattern of the mold is damaged, or a defect (error) is generated in the pattern formed on the substrate.
As the particles generated in the imprint apparatus, particles arising from sliding or friction caused by operating various actuators such as a stage and a conveying robot are considered. When the imprint material is supplied onto the substrate by an inkjet method, the imprint material which drifts as a mist may be dried and solidified, and then changed to particles. It is also considered that particles weakly attached to the obverse surface of each member at the time of assembling the imprint apparatus are removed from the obverse surface by a slight state change after operating the apparatus.
In particular, as one of mechanisms of attachment of the particles to the mold, there is a phenomenon in which the obverse surface of the mold is charged (charged separately) by releasing the mold from the imprint material on the substrate, and particles attached to the obverse surface of each member near the mold are attracted. For example, on a substrate stage which holds the substrate, various sensors and various marks are arranged, and a flat-plate member for controlling an airflow is further arranged so as to surround the periphery of the substrate. The particles generated in the imprint apparatus are attached to and accumulated on these obverse surfaces. The mold and the substrate stage are always close to each other, and the charged mold generates a strong electric field between itself and the substrate stage. This electric field makes particles that are weakly attached to the substrate stage attracted and attached to the mold.
To cope with this, Japanese Patent No. 4542167 proposes a technique of removing electric charges from a charged mold. Japanese Patent No. 4542167 discloses a technique of arranging a transparent conductive film on the pattern surface of the mold and by connecting this transparent conductive film to ground, removing electric charges generated on the pattern surface of the mold when releasing the mold from an imprint material on a substrate.
However, the technique disclosed in Japanese Patent No. 4542167 is insufficient to reduce attachment of the particles to the mold. For example, immediately after the mold is released from the imprint material on the substrate, electric charges exist in a member such as the imprint material facing the mold, generating an electric field between the member and these electric charges. Therefore, the particles are attracted and attached, in accordance to the polarity thereof, to the mold or the member facing the mold.
Further, the technique disclosed in Japanese Patent No. 4542167 needs the transparent conductive film on the pattern surface of the mold. It becomes necessary, however, to additionally deposit the transparent conductive film on a popular transparent mold (a mold made of quartz) whose processing method is established. This may cause an increase in a manufacturing cost and a decrease in a pattern accuracy. Further, considering application to the manufacture of a semiconductor device, an element present in a conductive film may move to a substrate side as a contamination, leading to a decrease in the electric characteristic of an electronic circuit.